Javascript variables inside if else statement

I have a custom volume bar and mute button in my music player. Muting is very simple, but I want to return the previous volume when the button is clicked for the second time.

Example: Let's say the current volume is at 50%. Clicking the mute button will change it to 0. Clicking it again should get it back to 50%.

This is how I tried it:

var music = document.getElementById('music');
var volumehead = document.getElementById('volume-head');
var volumebar = document.getElementById('volume-bar');
var mute = document.getElementById('mute');

mute.addEventListener("click", muteSound);

function muteSound(){
    if(mute.classList.contains('not-muted')){
        // Save current values before changing them
        var lastHead = volumehead.style.marginLeft;
        var lastVolume = music.volume;

        // Change classname for appearance and next click
        mute.className = "muted";

        // Change values to 0
        volumehead.style.marginLeft = "0px";
        music.volume = 0;
    } else {
        // Change classname for appearance and next click
        mute.className = "not-muted";

        // Use saved values
        volumehead.style.marginLeft = lastHead;
        music.volume = lastVolume;
    }
}

The 2 variables that hold the position of the handler and the volume are declared within the if-statement, meaning they're not accessible in the else-statement.

Declaring them outside of the statements means that the values will be "overwritten" by 0.

Is there a way to save the values and use them for the next click on the button?